Add combine_with_exported_module.

codegen/src/lib.rs

@@ -152,6 +152,20 @@ pub fn exported_module(module_path: proc_macro::TokenStream) -> proc_macro::Toke
     proc_macro::TokenStream::from(tokens)
 }
 
+#[proc_macro]
+pub fn combine_with_exported_module(args: proc_macro::TokenStream) -> proc_macro::TokenStream {
+    #[allow(unused_variables)]
+    let (module_expr, export_name, module_path) = match crate::register::parse_register_macro(args)
+    {
+        Ok(triple) => triple,
+        Err(e) => return e.to_compile_error().into(),
+    };
+    let tokens = quote! {
+        #module_path::rhai_generate_into_module(#module_expr);
+    };
+    proc_macro::TokenStream::from(tokens)
+}
+
 #[proc_macro]
 pub fn register_exported_fn(args: proc_macro::TokenStream) -> proc_macro::TokenStream {
     let (engine_expr, export_name, rust_modpath) = match crate::register::parse_register_macro(args)

codegen/src/module.rs

@@ -191,6 +191,7 @@ impl Parse for Module {
     }
 }
 
+#[allow(dead_code)]
 impl Module {
     pub fn attrs(&self) -> Option<&Vec<syn::Attribute>> {
         self.mod_all.as_ref().map(|m| &m.attrs)

codegen/src/rhai_module.rs

@@ -17,6 +17,7 @@ pub(crate) fn generate_body(
     let mut set_fn_stmts: Vec<syn::Stmt> = Vec::new();
     let mut set_const_stmts: Vec<syn::Stmt> = Vec::new();
     let mut add_mod_blocks: Vec<syn::ExprBlock> = Vec::new();
+    let mut set_mod_blocks: Vec<syn::ExprBlock> = Vec::new();
     let str_type_path = syn::parse2::<syn::Path>(quote! { str }).unwrap();
 
     for (const_name, const_expr) in consts {
@@ -54,6 +55,14 @@ pub(crate) fn generate_body(
             })
             .unwrap(),
         );
+        set_mod_blocks.push(
+            syn::parse2::<syn::ExprBlock>(quote! {
+                #(#cfg_attrs)* {
+                    self::#module_name::rhai_generate_into_module(m);
+                }
+            })
+            .unwrap(),
+        );
     }
 
     // NB: these are token streams, because reparsing messes up "> >" vs ">>"
@@ -137,6 +146,11 @@ pub(crate) fn generate_body(
                 #(#add_mod_blocks)*
                 m
             }
+            pub fn rhai_generate_into_module(m: &mut Module) {
+                #(#set_fn_stmts)*
+                #(#set_const_stmts)*
+                #(#set_mod_blocks)*
+            }
         }
     })
     .unwrap();

doc/src/plugins/module.md

@@ -24,6 +24,9 @@ use rhai::plugins::*;       // a "prelude" import for macros
 
 #[export_module]
 mod my_module {
+    // This constant will be registered as a the constant variable 'SOME_NUMBER'.
+    pub const SOME_NUMBER: i64 = 42;
+
     // This function will be registered as 'greet'.
     pub fn greet(name: &str) -> String {
         format!("hello, {}!", name)

doc/src/rust/packages/create.md

@@ -63,8 +63,8 @@ By far the easiest way to create a custom module is to call `Module::merge_flatt
 
 In fact, this exactly is how Rhai's built-in packages, such as `BasicMathPackage`, are implemented.
 
-`rhai::plugins::exported_module!` generates a module from the [plugins][plugin module] definition,
-and `Module::merge_flatten` consumes its, adding all its registered functions into the package itself.
+`rhai::plugins::combine_with_exported_module!` adds all functions and constants from the
+[plugins][plugin module] definition into the package itself.
 
 ```rust
 // Import necessary types and traits.
@@ -94,7 +94,10 @@ def_package!(rhai:MyPackage:"My own personal super package", module, {
     BasicArrayPackage::init(module);
     BasicMapPackage::init(module);
 
-    // Merge the plugin module into the custom package.
-    module.merge_flatten(exported_module!(my_module));
+    // Merge all registered functions and constants from the plugin module into the custom package.
+    //
+    // The text string name in the middle parameter can be anything and is reserved for future use;
+    // it is recommended to be an ID string that uniquely identifies the module.
+    combine_with_exported_module!(module, "my-functions", my_module));
 });
 ```

src/packages/arithmetic.rs

@@ -185,7 +185,7 @@ macro_rules! gen_signed_functions {
 
 macro_rules! reg_functions {
     ($mod_name:ident += $root:ident ; $($arg_type:ident),+ ) => { $(
-        $mod_name.combine_flatten(exported_module!($root::$arg_type::functions));
+        combine_with_exported_module!($mod_name, "arithmetic", $root::$arg_type::functions);
     )* }
 }
 
@@ -208,8 +208,8 @@ def_package!(crate:ArithmeticPackage:"Basic arithmetic", lib, {
     // Basic arithmetic for floating-point
     #[cfg(not(feature = "no_float"))]
     {
-        lib.combine_flatten(exported_module!(f32_functions));
-        lib.combine_flatten(exported_module!(f64_functions));
+        combine_with_exported_module!(lib, "f32", f32_functions);
+        combine_with_exported_module!(lib, "f64", f64_functions);
     }
 });
 

src/packages/array_basic.rs

@@ -58,7 +58,7 @@ macro_rules! reg_functions {
 }
 
 def_package!(crate:BasicArrayPackage:"Basic array utilities.", lib, {
-    lib.combine_flatten(exported_module!(array_functions));
+    combine_with_exported_module!(lib, "array", array_functions);
 
     reg_functions!(lib += basic; INT, bool, char, ImmutableString, FnPtr, Array, Unit);
 

src/packages/eval.rs

@@ -5,7 +5,7 @@ use crate::plugin::*;
 use crate::result::EvalAltResult;
 
 def_package!(crate:EvalPackage:"Disable 'eval'.", lib, {
-    lib.combine_flatten(exported_module!(eval_override));
+    combine_with_exported_module!(lib, "eval", eval_override);
 });
 
 #[export_module]

src/packages/fn_basic.rs

@@ -3,7 +3,7 @@ use crate::fn_native::FnPtr;
 use crate::plugin::*;
 
 def_package!(crate:BasicFnPackage:"Basic Fn functions.", lib, {
-    lib.combine_flatten(exported_module!(fn_ptr_functions));
+    combine_with_exported_module!(lib, "FnPtr", fn_ptr_functions);
 });
 
 #[export_module]

src/packages/logic.rs

@@ -45,7 +45,7 @@ macro_rules! gen_cmp_functions {
 
 macro_rules! reg_functions {
     ($mod_name:ident += $root:ident ; $($arg_type:ident),+) => { $(
-        $mod_name.combine_flatten(exported_module!($root::$arg_type::functions));
+        combine_with_exported_module!($mod_name, "logic", $root::$arg_type::functions);
     )* }
 }
 

src/packages/map_basic.rs

@@ -9,7 +9,7 @@ use crate::plugin::*;
 use crate::stdlib::vec::Vec;
 
 def_package!(crate:BasicMapPackage:"Basic object map utilities.", lib, {
-    lib.combine_flatten(exported_module!(map_functions));
+    combine_with_exported_module!(lib, "map", map_functions);
 });
 
 #[export_module]

src/packages/math_basic.rs

@@ -48,10 +48,10 @@ def_package!(crate:BasicMathPackage:"Basic mathematic functions.", lib, {
     #[cfg(not(feature = "no_float"))]
     {
         // Floating point functions
-        lib.combine_flatten(exported_module!(float_functions));
+        combine_with_exported_module!(lib, "float", float_functions);
 
         // Trig functions
-        lib.combine_flatten(exported_module!(trig_functions));
+        combine_with_exported_module!(lib, "trig", trig_functions);
 
         reg_functions!(lib += basic_to_float::to_float(INT));
 

src/packages/string_more.rs

@@ -57,7 +57,7 @@ def_package!(crate:MoreStringPackage:"Additional string utilities, including str
     #[cfg(not(feature = "no_float"))]
     reg_functions!(lib += float; f32, f64);
 
-    lib.combine_flatten(exported_module!(string_functions));
+    combine_with_exported_module!(lib, "string", string_functions);
 
     lib.set_raw_fn(
         "pad",

src/packages/time_basic.rs

@@ -21,7 +21,7 @@ use instant::Instant;
 
 def_package!(crate:BasicTimePackage:"Basic timing utilities.", lib, {
     // Register date/time functions
-    lib.combine_flatten(exported_module!(time_functions));
+    combine_with_exported_module!(lib, "time", time_functions);
 });
 
 #[export_module]

tests/plugins.rs

@@ -1,5 +1,6 @@
 #![cfg(not(any(feature = "no_index", feature = "no_module")))]
 
+use rhai::module_resolvers::StaticModuleResolver;
 use rhai::plugin::*;
 use rhai::{Engine, EvalAltResult, INT};
 
@@ -10,6 +11,8 @@ mod test {
     pub mod special_array_package {
         use rhai::{Array, INT};
 
+        pub const MYSTIC_NUMBER: INT = 42 as INT;
+
         #[cfg(not(feature = "no_object"))]
         pub mod feature {
             use rhai::{Array, Dynamic, EvalAltResult};
@@ -66,7 +69,7 @@ fn test_plugins_package() -> Result<(), Box<EvalAltResult>> {
     let mut engine = Engine::new();
 
     let mut m = Module::new();
-    m.combine_flatten(exported_module!(test::special_array_package));
+    combine_with_exported_module!(&mut m, "test", test::special_array_package);
     engine.load_package(m);
 
     reg_functions!(engine += greet::single(INT, bool, char));
@@ -83,5 +86,14 @@ fn test_plugins_package() -> Result<(), Box<EvalAltResult>> {
         "6 kitties"
     );
 
+    let mut resolver = StaticModuleResolver::new();
+    resolver.insert("test", exported_module!(test::special_array_package));
+
+    engine.set_module_resolver(Some(resolver));
+    assert_eq!(
+        engine.eval::<INT>(r#"import "test" as test; test::MYSTIC_NUMBER"#)?,
+        42
+    );
+
     Ok(())
 }